From cb731548fa8f78c4deec94dce12c6af59c2b033a Mon Sep 17 00:00:00 2001
From: John McCall <rjmccall@apple.com>
Date: Sun, 11 Jun 2017 20:33:00 +0000
Subject: [PATCH] Don't crash when forming a destructor name on an incomplete
 type.

Fixes PR25156.

Patch by Don Hinton!

llvm-svn: 305169
---
 clang/lib/Sema/SemaExprCXX.cpp          | 9 ++++++---
 clang/test/SemaCXX/nested-name-spec.cpp | 7 +++++++
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
index 00a4b39f1423..a9ff21bc41ab 100644
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -189,12 +189,15 @@ ParsedType Sema::getDestructorName(SourceLocation TildeLoc,
     // have one) and, if that fails to find a match, in the scope (if
     // we're allowed to look there).
     Found.clear();
-    if (Step == 0 && LookupCtx)
+    if (Step == 0 && LookupCtx) {
+      if (RequireCompleteDeclContext(SS, LookupCtx))
+        return nullptr;
       LookupQualifiedName(Found, LookupCtx);
-    else if (Step == 1 && LookInScope && S)
+    } else if (Step == 1 && LookInScope && S) {
       LookupName(Found, S);
-    else
+    } else {
       continue;
+    }
 
     // FIXME: Should we be suppressing ambiguities here?
     if (Found.isAmbiguous())
diff --git a/clang/test/SemaCXX/nested-name-spec.cpp b/clang/test/SemaCXX/nested-name-spec.cpp
index 6ae45ff63332..725ac64cedb7 100644
--- a/clang/test/SemaCXX/nested-name-spec.cpp
+++ b/clang/test/SemaCXX/nested-name-spec.cpp
@@ -169,6 +169,13 @@ void N::f() { } // okay
 struct Y;  // expected-note{{forward declaration of 'Y'}}
 Y::foo y; // expected-error{{incomplete type 'Y' named in nested name specifier}}
 
+namespace PR25156 {
+struct Y;  // expected-note{{forward declaration of 'PR25156::Y'}}
+void foo() {
+  Y::~Y(); // expected-error{{incomplete type 'PR25156::Y' named in nested name specifier}}
+}
+}
+
 X::X() : a(5) { } // expected-error{{use of undeclared identifier 'X'}}
 
 struct foo_S {